Short-range ordered photonic structures of lamellae-forming diblock copolymers for excitation-regulated fluorescence enhancement

Abstract

Photonic crystals can be represented by periodic nanostructures with alternating refractive indices, which create artificial stop bands with the appearance of colors. In this regard, nanodomains of block copolymers and the corresponding structural colors have been intensively studied in the past. However, the practical application of photonic crystals of block copolymers has been limited to a large degree because of the presence of large defects and grain boundaries in the nanodomains of block copolymers. The present study focuses on the alternative opportunity of short-range ordered nanodomains of block copolymers for fluorescence enhancement, which also has a direct relevance to the development of fluorescence sensors or detectors. The enhancement mechanism was found to be interconnected with the excitation process rather than the alternation of the decay kinetics. In particular, we demonstrate that randomly oriented, but regular grains of lamellae of polystyrene-block-polyisoprene, PS-b-PI, diblock copolymers and their blend with PS homopolymers can behave as Bragg mirrors to induce multiple reflections of the excitation source inside the photonic structures. This process in turn significantly increases the effective absorption of the given fluorophores inside the polymeric photonic structures to amplify the fluorescence signal.

Emission Enhancement of Fluorescent Molecules by Antireflective Arrays

“…Many researchers have employed this method and achieved a series of successful results [24–27]. However, the enhancement requires that the maximum excitation or emission of fluorescence molecule should match with the photonic crystal reflection, which restricts these techniques from practical applications [28–30]. The antireflective arrays can enhance the absorption of light in a wide range of wavelengths due to reducing the surface reflective [31–36].…”

One‐Step Hierarchical Assembly of Spheres‐in‐Lamellae Nanostructures from Solvent‐Annealed Thin Films of Binary Diblock Copolymer Micelles

“…From the previous success of BCPs in nanotechnology, scientist in the field continued to pursue the formation of multifunctional assemblies by utilizing mixed BCP nanostructures . In fact, this attempt, in large part, arose from the experimental observation that optical, electrical, and catalytic functionalities can often be combined to induce synergistic effects, which would be promising for many applications . For instance, Kim and co‐workers prepared hierarchically assembled Au and Pt nanoparticles from coexisted nanodomains of polystyrene‐ block ‐poly(4‐vinyl pyridine) (PS‐P4VP) copolymers .…”

“…This multifunctional assembly enabled us to study the plasmonic effects of metal nanoparticles on the nearby fluorophores, which has relevance in sensing applications. In another example, when dye‐containing PS‐P4VP micelles were homogenously placed inside photonic crystals of PS‐PI lamellae, the incident light could be continuously reflected inside the photonic structures to enhance the light absorption and fluorescence of dyes . From these examples, one may anticipate that enormous opportunities would be present in the hierarchical assembly from the viewpoints of structure, material properties, and device performance.…”

Reactive block copolymers for patterned surface immobilization with sub-30 nm spacing

“…We reported very recently a library of mono-or bifunctional PMMA-b-PS BCPs and their self-assembly behavior in thin films, where minor changes in spacing were generally observed. 46 In parallel, we have been working on lamellaeforming polystyrene-block-polyisoprene (PS-b-PI)a very wellknown phase-segregating system [47][48][49][50][51][52][53][54] which has been modified in the PS block with a variety of functional comonomers. Various styrenic derivatives are commercially available or readily synthesized, while polyisoprene possesses inherent reactivity through the remaining double bonds present after synthesis.…”